, We thank Christine Vallet-Coulomb (CEREGE, France) for the isotope analysis of modern Lake Petit waters and Pauline Chaurand (CEREGE, France) for providing help with the micro-XRF measurements. Thanks to Alain Tonetto (Aix-Marseille University) for managing the SEM in Marseille. Coring of Lake Petit, 2009 and 2012) was made possible thanks to Fabien Arnaud (EDYTEM), Charline Giguet-Covex (EDYTEM), Emmanuel Malet (EDYTEM)

, Jérome Poulenard (EDYTEM) and Bruno Wilhelm (LTHE)

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